“My great hope is that TESS will find new mysteries,” said Dr. Stephen Rinehart, a project scientist for the mission at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Maybe we’ll find something out there that nobody expected and will leave people scratching their heads.”

NASA's Transiting Exoplanet Survey Satellite (TESS) launch is the next step in the search for planets outside of our solar system that will study and document 200,000 of the brightest stars near the sun to search for any transiting exoplanets. Of these, some 300 are expected to be Earth-sized and super-Earth-sized exoplanets, which are worlds no larger than twice the size of Earth.

“One of the biggest questions in exoplanet exploration is: If an astronomer finds a planet in a star’s habitable zone, will it be interesting from a biologist's point of view?” said George Ricker, TESS principal investigator at the Massachusetts Institute of Technology (MIT) Kavli Institute for Astrophysics and Space Research in Cambridge, which is leading the mission. “We expect TESS will discover a number of planets whose atmospheric compositions, which hold potential clues to the presence of life, could be precisely measured by future observers.”

The stars being studied by TESS are between 30 to 100 times brighter than those surveyed by the Kepler and K2 missions and TESS will cover a sky area 400 times larger than that monitored by Kepler.The TESS launch is scheduled for 18:32 EDT (23:32 BST) and will be broadcast live on NASA TV. The TESS launch overview will begin at 11:00 followed by the prelaunch news conference at 13:30 EDT, a science news conference from 15:00 EDT and then live coverage from the countdown will run from 18:00 to 20:00.

TESS will launch from Space Launch Complex 40 at Cape Canaveral Air Force Station, as long as the weather is "favourable", on board at SpaceX Falcon 9 rocket.

For the next two years, TESS will survey the sky, breaking it into 26 sections, each 24 degrees by 96 degrees across, specficially looking for exoplanets that periodically block part of the light from their host stars. These events are called transits, hence TESS' name. Powerful cameras on TESS will monitor each section for at least 27 days at a time, looking at the brightest stars.

Depending on available light, NASA can determine the size of the star as well as its planets and the length of orbits, which can give an indication of the planet's proximity to the star, which in turn can help experts determine the conditions on that planet and the chance of it supporting life.

“TESS is opening a door for a whole new kind of study,” said Stephen Rinehart, TESS project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, which manages the mission. “We’re going to be able study individual planets and start talking about the differences between planets. The targets TESS finds are going to be fantastic subjects for research for decades to come. It’s the beginning of a new era of exoplanet research.”

After the TESS launch has compiled a list of candidate exoplanets, ground-based surveys, using telescopes here on Earth, will use this data to look at each planet's composition to see if they're rocky, like Earth, or gas giants like Jupiter. TESS will likely find exoplanets of a kind we've never seen before.

“TESS will be able to say: there’s an interesting system for the Webb telescope, and then it can move on and find another one,” Ricker said. “It’s really a scout for this whole process.”

“We learned from Kepler that there are more planets than stars in our sky, and now TESS will open our eyes to the variety of planets around some of the closest stars,” said Paul Hertz, Astrophysics Division director at NASA Headquarters. “TESS will cast a wider net than ever before for enigmatic worlds whose properties can be probed by NASA’s upcoming James Webb Space Telescope and other missions.”